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Software => Software => Topic started by: javila on September 10, 2010, 01:11:26 AM

Title: Problems with PWM on webbotlib
Post by: javila on September 10, 2010, 01:11:26 AM

Hello:
I am currently trying to use pwm with webbolib to control two motors but I am having trouble picking the right frequencies.
I am using this:
void appInitHardware(void){
pwmInitHertz(B2,9000,100,null);}
To set the frequency to 9k in this case. It seems that when I use anything above 9000, the microcontroller does not work properly. Can any of you tell me how I can calculate the range of frequencies that I can use, and how do I check that the frequency is being set properly. I know that that function is a Boolean function but do not know how to use it to check. Any example would be appreciated. ( I know that there is a motorpwm function but I am using a different  pin configuration than the one required by that function).
I have a atmega328p, with a 18432000 Hz crystal connected to a L298

Thanks in advance

Title: Re: Problems with PWM on webbotlib
Post by: Webbot on September 10, 2010, 03:50:07 PM

Try using Solarbotics/L298.h http://webbot.org.uk/WebbotLibDocs/34638.html (http://webbot.org.uk/WebbotLibDocs/34638.html) as thats just a fairly generic L298 implementation.

Title: Re: Problems with PWM on webbotlib
Post by: Webbot on September 10, 2010, 03:56:15 PM

Alternatively: change the last parameter ie

Code: [Select]

// Allow use of %lu to print uint32_t values
// Put this right at the top of your program
#define RPRINTF_COMPLEX
#include "rprintf.h"

uint32_t actualHz;
if(pwmInitHertz(B2,9000,100, &actualHzl)){
   // PWM is on and 'acutalHz' has the value
   rprintf("Actual PWM freq=%lu\n",actualHz);
}else{
  // PWM failed, maybe the pin doesn't support PWM
  // or the timer is already used to do other stuff
}

Title: Re: Problems with PWM on webbotlib
Post by: javila on September 10, 2010, 04:41:32 PM

thanks, that is really useful.